Vertically aligned carbon nanotube (VACNT) films have promising applications in solar cells, radiometers, and photonic devices. We have fabricated VACNT films with thicknesses of 10, 36, 45, and 120 μm on silicon substrates. The absorption coefficient of each film is obtained from the measured regular transmittance from 1 to 19 μm wavelengths, using a ratio method. The degree of alignment of the VACNT films is estimated by comparison of experiments with an analysis based on the effective medium theory. The effect of thickness on the absorption coefficient of the VACNT films is elucidated according to their morphologies.
Bibliographical noteFunding Information:
This work was supported by the Department of Energy (DE-FG02-06ER46343). H.Y. acknowledges the support from the National Basic Research Program of China (2009CB939900) and the program of Study Abroad for USTC Sponsored Outstanding Young Teachers.